Terminal Block Jumpering (Cross-Connection)

Terminal Block Jumper Types

There are many types of DIN rail mounted electrical terminal blocks and, as a result, there are numerous types of inter-terminal current jumpering options available (also known as cross-connection). The most common types include:

• A current bar placed across the top of the terminal block with screws that connect to the terminal block via a jumper sleeve. This is the “SAK” jumpering system.
• An integrated jumper (or cross-connection) that is screwed into place across the top of adjacent terminal blocks. This style of jumper is integrated and self-contained. It consists of insulation, current bar, and fixing screws. Jumpering points that are not required are clipped off. This is the “W-Series” jumpering or cross-connection system.
• A jumper “comb” that is inserted into the same connection place as the wire. These jumper combs may be available with or without protective insulation.
• Plug-in type jumpers that are inserted from the top of the terminal block. This type of jumper inserts into a slot in the terminal block current bar. The ends of the jumper bar are designed so that the prong on the tip of the jumper will create spring tension and remain fixed in the terminal block current bar.

Power Design Considerations

Remember to compute the additive current that will be conducted through the jumper bar regardless of the type selected. If power is fed from one end, the current at that end will be the sum of all the individual currents of the connected blocks. If power is fed from the middle the maximum current exposure of the jumper will be reduced.

Comb-Type Terminal Block Jumpers

“Comb” type jumpers are convenient because they can readily be clipped or broken off to skip over some terminal blocks. They are available in multi-pole versions of 58 or even 75 poles. The down side is that they are installed in the same place where the wiring connection goes and therefore competes for space in the terminal block. Care must be taken to insure that the wire is securely fixed in the terminal block if it shares space with a jumper “comb”.

Screw-in Terminal Block Jumpers

Both the SAK style and W-Series style jumpers use captive screws with locking washers to insure a positive connection to the current bar. These types of jumpers do not compete with the wiring for space or compromise the ability to secure the wiring. Once secured, these jumpers are very stable. However, during installation it is easy to miss a screw or not tighten it adequately. This could result in a faulty connection. Jumper sleeves can be removed from the SAK style jumpers and poles can be cut off of the W-Series style jumpers to allow some terminal blocks to be skipped.

Plug-in Terminal Block Jumpers